There is a configure test "for libc-friendly stddef.h", which sets a
makefile variable stddef.h that appears to be nowhere used. It
appears the uses of this variable were removed by:
Tue Feb 21 00:10:50 1995 Roland McGrath <roland@churchy.gnu.ai.mit.edu>
* Makefile (headers): Remove $(stddef.h).
* Makeconfig (stddef.h): Variable removed; now require gcc version
>= 2.2.
* stddef.h: File removed.
(having been added by
Wed May 26 14:44:19 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* configure.in (autoconf checks): Add new check for a
libc-friendly stddef.h.
so the test was of use for less than two years, before being obsolete
for over 20 years). This patch removes the test.
Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).